1. Field of the Invention
The present invention relates to eyewear, and, more particularly, to eyewear with slidable auxiliary lenses.
2. Description of the Related Art
Common vision conditions correctable by eyewear include nearsightedness (myopia) in which close objects are seen clearly, but objects farther away appear blurred; farsightedness (hyperopia) in which distant objects are seen clearly, but close objects are not; astigmatism in which blurred vision is caused by an irregular shape of the cornea; and presbyopia in which the lens of the eye becomes less flexible, making focusing on close objects more difficult.
For the vast majority of adults in their 40's and beyond, some degree of presbyopia is present. Frequently, multiple vision conditions are diagnosed, and it is not uncommon to need vision correction for presbyopia as well as hyperopia, and/or astigmatism. Because corrective lens are different for each of these conditions, many people resort to having more than one pair of eyeglasses, such as a pair of eyeglasses for reading and another for driving (to see long distances). Indeed, many people also require eyeglasses to optimize viewing of a computer screen. Additionally, many people find sunglasses useful for driving or outdoor usage. While prescription lens can be tinted, these “prescription sunglasses” will have the same limitations as above, i.e., the user will have to switch to another pair of eyeglasses when a different vision correction is required.
For some, having to own and use several pairs of eyeglasses is inconvenient. If one owns more than a single pair of glasses, it will be necessary to carry all of them around. It will be necessary to find the proper pair of glasses and change to it when needed.
An early innovation in the art was the bifocal lens, which is credited to Benjamin Franklin. A bifocal lens divides a lens into an upper portion and a lower portion, each having a different corrective lens. Accordingly, a user need not have to use separate eyeglasses. Usually, the bottom lens will be for close up viewing (such as reading). Additionally, trifocal lens have been developed that divide the lens into three segments, each having a different corrective lens. Although bifocals/trifocals are used, there is a feeling among some that these eyeglasses are not stylish.
To remedy the problem of style, so-called progressive lens were developed. Progressive lens eliminate the conspicuous line (or lines) that separates the lenses. However, as with bifocals/trifocals, some users report headaches and dizziness. Still others report that it is difficult to adjust their eyes to the proper area of the lenses to use.
Another approach has been to provide auxiliary lenses for placement over the primary lenses. An example is to provide clip-on lenses for reading or tinted clip-on lenses to transform the eyewear to sunglasses. In addition to clipping-on, other ways of attaching the auxiliary lens have been developed. For example, U.S. Pat. No. 6,352,342 to Huang discloses an auxiliary eyewear frame magnetically attachable to the primary frame. As another example, U.S. Pat. No. 6,942,337 to Zelman discloses eyewear having both a primary lens frame and an auxiliary lens frame separately coupled to an eyewear platform. Although useful, both devices are relatively complex and require the user to assemble the device.
Another approach is to structure the temples of the eyewear to store auxiliary lenses, as disclosed in U.S. Pat. No. 4,666,266 to Morrison. Although storage of the auxiliary lens along the side of the eyeglasses (temple) is useful, the auxiliary lens of Morrison must be bent around the hinge portion of the frame through a continuous “channel” when deployed; therefore, they can only be made of a thin, flexible material. As such, the auxiliary lenses will have limited corrective ability, optical quality and practical value.